Semantic network
A semantic network, or frame network, is a network which represents semantic relations between concepts. This is often used as a form of knowledge representation. It is a directed or undirected graph consisting of vertices, which represent concepts, and edges. History In 1909, Charles S. Peirce proposed a graphical notation of nodes and edges called "existential graphs" that he called "the logic of the future". This began the debate between advocates of "logic" and advocates of "semantic networks." This debate obscured the fact that semantics networks, at least those with well-defined semantics, are a form of logic. "Semantic Nets" were first invented for computers by Richard H. Richens of the Cambridge Language Research Unit in 1956 as an "interlingua" for machine translation of natural languages. They were developed by Robert F. Simmons and M. Ross Quillian Quillian, R. A notation for representing conceptual information: An application to semantics and mechanical English para- phrasing. SP-1395, System Development Corporation, Santa Monica, 1963. at System Development Corporation in the early 1960s. It later featured prominently in the work of Allan M. Collins and Quillian (e.g., Collins and Quillian; Collins and Loftus Quillian Quillian, M. R. (1967). Word concepts: A theory and simulation of some basic semantic capabilities. Behavioral Science, 12(5), 410-430.Quillian, M. R. (1968). Semantic memory. Semantic information processing, 227–270.Quillian, M. R. (1969). The teachable language comprehender: a simulation program and theory of language. Communications of the ACM, 12(8), 459-476.Quillian, R. Semantic Memory. Unpublished doctoral dissertation, Carnegie Institute of Technology, 1966.) Basics of semantic networks Definition A semantic network is used when one has knowledge that is best understood as a set of concepts that are related to one another. More generally Most semantic networks are cognitively based. They also consist of arcs and nodes which can be organized into a taxonomic hierarchy. Semantic networks contributed ideas of spreading activation, inheritance, and nodes as proto-objects. They are intractable for large domains. Finally they don't represent performance or meta-knowledge very well. Things to remember about semantic networks Some properties are not easily expressed using a semantic network, e.g., negation, disjunction, and general non-taxonomic knowledge. Expressing these relationships requires workarounds, such as having complementary predicates and using specialized procedures to check for them, but this can be regarded as less elegant. Semantic networks are a common type of machine-readable dictionary. Important semantic relations: * Meronymy (A is part of B) * Holonymy (B has A as a part of itself) * Hyponymy (or troponymy) (A is subordinate of B; A is kind of B) * Hypernymy (A is superordinate of B) * Synonymy (A denotes the same as B) * Antonymy (A denotes the opposite of B) WordNet An example of a semantic network is WordNet, a lexical database of English. It groups English words into sets of synonyms called synsets, provides short, general definitions, and records the various semantic relations between these synonym sets. Some of the most common semantic relations defined are meronymy (A is part of B, i.e. B has A as a part of itself), holonymy (B is part of A, i.e. A has B as a part of itself), hyponymy (or troponymy) (A is subordinate of B; A is kind of B), hypernymy (A is superordinate of B), synonymy (A denotes the same as B) and antonymy (A denotes the opposite of B). WordNet properties have been studied from a network theory perspective and compared to other semantic networks created from Roget's Thesaurus and word association tasks. From this perspective the three of them are a small world structure. It is also possible to represent logical descriptions using semantic networks such as the existential Graphs of Charles Sanders Peirce or the related Conceptual Graphs of John F. Sowa. These have expressive power equal to or exceeding standard first-order predicate logic. Unlike WordNet or other lexical or browsing networks, semantic networks using these representations can be used for reliable automated logical deduction. Some automated reasoners exploit the graph-theoretic features of the networks during processing. Other examples Other examples of semantic networks are Gellish models. Gellish English with its Gellish English dictionary, is a formal language that is defined as a network of relations between concepts and names of concepts. Gellish English is a formal subset of natural English, just as Gellish Dutch is a formal subset of Dutch, whereas multiple languages share the same concepts. Other Gellish networks consist of knowledge models and information models that are expressed in the Gellish language. A Gellish network is a network of (binary) relations between things. Each relation in the network is an expression of a fact that is classified by a relation type. Each relation type itself is a concept that is defined in the Gellish language dictionary. Each related thing is either a concept or an individual thing that is classified by a concept. The definitions of concepts are created in the form of definition models (definition networks) that together form a Gellish Dictionary. A Gellish network can be documented in a Gellish database and is computer interpretable. Such networks involve fairly loose semantic associations that are nonetheless useful for human browsing. It is possible to represent logical descriptions using semantic networks such as the Existential Graphs of Charles S. Peirce or the related Conceptual Graphs of John F. Sowa. These have expressive power equal to or exceeding standard first-order predicate logic. Unlike WordNet or other lexical or browsing networks, semantic networks using these can be used for reliable automated logical deduction. Some automated reasoners exploit the graph-theoretic features of the networks during processing. Software tools "Semantic Nets" were first invented for computers by Richard H. Richens of the Cambridge Language Research Unit in 1956 as an "interlingua" for machine translation of natural languages. They were developed by Robert F. Simmons at Systems Development Corporation, Santa Monica, California in the early 1960s and later featured prominently in the work of M. Ross Quillian in 1966. There are also elaborate types of semantic networks connected with corresponding sets of software tools used for lexical knowledge engineering, like the Semantic Network Processing System ( SNePS ) of Stuart C. Shapiro or the MultiNet paradigm of Hermann Helbig (MultiNet is an acronym for "Multilayered Extended Semantic Network"). The latter is especially suited for the semantic representation of natural language expressions and used in several NLP applications. One can consider a mind map to be a very free form variant of a semantic network. By using colors and pictures the emphasis is on generating a semantic net which evokes human creativity. In the 1960s to 1980s the idea of a semantic link was developed within hypertext systems as the most basic unit, or edge, in a semantic network. These ideas were extremely influential, and there have been many attempts to add typed link semantics to HTML and XML. See also * Abstract semantic graph * Conceptual graph * Entitative graph * Existential graph * Information space * Knowledge representation * Logical graph * Semantic lexicon * Semantic Web * Semantics * Semantic computing * Semantic neural network * Semiotics * Topic map * Unified Medical Language System (UMLS) Examples * Lexipedia * WordNet * SNOMED CT * ConceptNet References Further reading * Allen, J. and A. Frisch (1982). "What's in a Semantic Network". In: Proceedings of the 20th. annual meeting of ACL, Toronto, pp. 19-27. * John F. Sowa, Alexander Borgida (1991). Principles of Semantic Networks: Explorations in the Representation of Knowledge External links * Semantic networks John F. Sowa's article on various kinds of semantic networks * What Are Semantic Networks? A Little Light History * MultiNet and its software environment * WordNet® - lexical reference system * ConceptNet Knowledge Browser and Commonsense Inference API * Semantic MediaWiki (Experimental Wikimedia project using variable namespaces in place of our Categories) * SNePS SNePS Research Group Homepage Category:Semantics Category:Semantic web Category:Knowledge representation Category:Networks